[Ifeffit] limits for second shell

Hi, thanks for the help. Let me be more clear. I am trying to know the limits to use information from the second shell, from XRD I found that the phase is present, but I want to know if I can use the signal to obtain more information about second neighbors. I have this sample and some more where I find a second shell signal, the doubt is about how far can I trust in this information, is there a limit in k-space to believe in the information of the second shell and try to fit it? I attach the R-space graph with the same limits for the FT, there are still differences, what should I check to be sure the information I can get from the second shell is trustable and not a problem of the noisy signal? Thanks, euG